Functional opiate receptor in mouse vas deferens: evidence for a complex interaction
Sánchez-Blázquez, P.; Garzón, J.; Lee, N.M.
Journal of Pharmacology and Experimental Therapeutics 226(3): 706-711
1983
ISSN/ISBN: 0022-3565 PMID: 6310079 Document Number: 216713
Treatment of the isolated mouse vas deferens with the enzyme arylsulfatase (E.C. 3.1.6.1) effected the ability of this tissue to respond to various opiates. It increased the IC50 , levorphanol and normorphine. There was no effect on the action of etorphine, .beta.-endorphin or dynorphin. With morphine there was a biphasic effect, IC50 values increasing at low enzyme concentrations and decreasing at high enzyme concentrations. A further comparison of arylsulfatase effects on morphine and on D-Ala2-D-Leu5-enkephalin indicated that the morphine effect, unlike the D-Ala2-D-Leu5-enkephalin effect, could not be reversed by washing and that morphine, unlike D-Ala2-D-Leu5-enkephalin, became much less sensitive to naloxone antagonism. The observed modifications in the shape of the dose-response curves indicate that the effect of the opiates in the mouse vas deferens is more complex than that expected through the occupation of a simple receptor. There is either more than 1 type of functional receptor for each agonist or only 1 receptor which can interact with every drug in different ways; this complexity is discussed in terms of various possibilities, including fractional occupancy, positive cooperativity and multiple sits.